Radiodevice



April 9, 1935. R. F.'ZIMMERMAN ET AL 1,996,847

RADIODEVICE Filed NOV. 18, 1952 2 Sheets-Sheet 1 INVENTORS April 1935. R. F. ZIMMERMAN T AL 1,996,847

RADIODEVICE Filed Nov. 18, 1932' 2 Sheets-Sheet 2 A 'L E-uE-WIIM. m

)zv VENTOJES Jaw 14 W Patented Apr. 9, 1935 PATENT OFFlCE Robert' l Zimmerman and Herbert W. De Weese; Dayton; Ohio, assignors of sixty per cent to said Zimmerman and for Weese I ty per cent to said De ApplicationNovember 18, 1932, Serial No. 643,229

7 Claims.

This invention relates to-a, radio device, and: more particularly to a device for mixing signals.-

withgenerated oscillations to produce a beatfrequency signal.

a device that is comparatively simple in structure and easily attachable to a conventional or ordinary type oflonger wave or broadcast receiver to adapt said receiver for the reception of shorter wave signals.

Another object of the presentinvention is to provide a short wave adapter for an ordinary or conventional broadcast receiver that is inexpensive to build as well as easy to install.

a short wave adapter for an ordinary or conventional broadcast receiver that does not necessitate material changes in the circuit or structure of the broadcast receiver in order to be installed therewith.

Another object of this invention is to. provide acircuit for mixing signals withoscillations generated within said circuit that is efiicient and stable in operation as well as void of unnecessary complexities.

Another object of the present invention is to provide a circuit for a radio device having an.

oscillating thermionic tube therein, that permits control of the frequency of the oscillations and that generatesharmonic oscillations and utilizes these harmonic oscillations in. the reception of signals in different frequency bands.

Another object of the. present invention is to provide a circuit for a.device to be used Lrcon;

I junction with an ordinary or conventionalir'a dio;

receiver in thereceptionof short wave signals that permits the reception of eithershort wave. or broadcast signals without change of physical connections between the device andthe receiver.

Another object of the present invention is to provi'daacircuit.forfladevice to be used in conjunction with an ordinary or. conventional radio receiver in the reception 'of short wave-signals that lends itself. to neatness and compactness .of design into a unitary structure.

Another object of the present invention is to provide a circuit for a device for mixing signals with oscillations generated therein, that eliminates the necessity of voltages of detrimental magnitude between the inductances utilized-in the circuit, and between theturns of the individual inductances.

Another object of the present invention is to provide a circuit fora device for mixing signals with oscillations generated therein, that permits An object of the present invention isfto provide.

Another object of this invention is to provide a common low potential connection between the inductances utilized.

Another object of this invention is to provide a device that utilizes the shield element therefor as a base, and housing for the parts thereof.

Another object of the present invention is to provide an improved method of receiving signals in different short Wave bands.

Another object of the present invention is'to provide a method of receiving a warning or notice of the transmission of a local short wave station while listening to a broadcast program.

Other objects and advantages of this invention will be apparent from the accompanying specification and drawings wherein a preferred form of. the present invention is clearly'illustrated and described.

In the drawings:

Fig. l is a wiring diagram showing a circuit ofa preferred form of the present inventiomwith formof construction of the present invention.

Fig. 4 is a bottom view with the cover removed. showing the, arrangement and mounting. of the 30 Fig. 5 is a perspective view of a preferred formof inductance unit for use in the present device.

parts in a unit such as that shown inFig. 3.

,Fig. 6 isa detail View of the subassembly employed in a unit such as that shown in Fig. 4,

with some parts shown in section and somein elevation.

With particular nail is connected to one end of an inductance or tuning coil it! thru a lead 2,-and to one end of an inductance or primary coil-l2; The other end ofthe inductance or tuning coil-l0 is coupled or connected to a grid or controlelectrode l4 ofqa thermionic tube l6 thru a condenser I3. A resistor zilt is connected across the condenser l8, and the condenser !8 and resistor 2il-form a grid condenser and grid leale. A variable condenser 22. is con.-

nected across the inductance. liiforming a tun.

able resonant circuit l for accomplishing the tununderstood to refer .to any standard type of re'-- celver capable of. receiving longer wavesignals diagram showing a modifica.-

reference to Fig. 1, an anten--- ing- The other. end of the inductance or primary;

than are to be received thru the use of the present invention in combination therewith. Since that receiver is not a part of the present invention, but may be of most any type or make well known to those skilled in the art, only the parts of the circuit have been shown that indicate an example of the connections thereto. In the exemplary portion of the input circuit of a broadcast receiver that is shown, the antenna binding post or terminal H is connected to one end of a primary coil 13 of an antenna coupling unit I1. The other end of the primary coil [3 is connected to ground at 15. The primary coil 13 is magnetically coupled witha secondary coil I9 of the coupling unit I7, and. that secondary coil 19 has a variable condenserZl connectedthereacross to form a turnable resonant circuit 23 for tuning the broadcast receiver to a predetermined or desired frequency. One end of the secondary coil 19 is connected to an inputor control electrode 25 of a thermionicamplifier tube 21. The thermionic amplifier tube 2'! has beside the input or control electrode, an anode element 29, an auxiliary grid element 3|, a cathode element 33, and a heater element 35 therein, and all of said elements as well as the other end of the secondary coil [9 are provided with suitable leads for connection to the remainder of the circuit of the broadcast receiver.

An inductance or feed-back coil 26 is magnetically coupled with the primary coil or inductance l2, and has one of its ends connected to a cathode or electron emitting element 28 of the thermionic tube I 6. The other end of the inductance or feedback coil 26 is connected to the antenna I and to a shield element 36. There is also magnetic coupling between the inductances i2 and 26 and the inductance Ii). However, the inductances l2 and 26 are in closer magnetic, relation than the inductances 26 and I6 or the inductances i2 and An anode or plate electrode 32 of the thermionic tube I 6 is connected to an auxiliary or screen grid 34 of that tube thru a resistor 36, and to a suitable lead 38 which lead is adapted to be connected to a suitable source of potential on a standard broadcast receiver. That source of potential is preferably the potential obtained from an anode or screen grid of one of the tubes in the broadcast receiver, or directly from the anode potential supply circuit of the broadcast receiver. As shown as an example, the lead 38 is connected to an auxiliary or screen grid 39 of a thermionic amplifier tube 4| of the broadcast receiver. This is one preferred source because the potential thus obtained is practically constant, and is easily accessible by making conplifier tube 4| has therein, beside the auxiliary or screen grid 39 and the anode 43, an auxiliary grid 59, a control grid 6| and a filament 63. The auxiliary grid 59 is connected to the mid point of the filament 63, while the control grid 6| and filament 63 are provided with suitable leads for connection to the remainder of the refer to corresponding parts.

circuit of the broadcast receiver. The condensers 65 and 61 connected to the anode 43 and screen grid 39 respectively, and to ground at 69 and II respectively are by-pass condensers. A heater element 46 of the thermionic tube I6 is connected to suitable leads 42 and 44, which leads are adapted to be connected to a suitable source of potential on the broadcast receiver which is preferably the source of heater potential for the tubes of the broadcast receiver that are designed for the same heater voltage. As shown, they are connected to the heater element 35 of the thermionic tube 21. This is convenient, because the connections of the leads 42 and 44 may be made to the heater prongs of the tube 27.

With particular reference to Fig. 2, an inductance or primary coil 50 has one end connected to the antenna I and its other end connected to a suitable lead 24 adapted to be connected to the antenna post or terminal of a conventional broadcast receiver. An inductance or tunin coil 52 has one end connected to a grid or control electrode 54 of a thermionic tube 56 thru a condenser 58, and its other end connected to the shield element 36 and to ground at 62 thru a suitable lead 60. A variable or tuning condenser 22 is connected across the inductance 52 to form a tunable resonant circuit 6 and accomplish the tuning of that inductance. A resistor 64 is connected to the grid or control electrode 54 and to the lead 69. An inductance or feed-back coil 66 is magnetically coupled with the inductance or primary coil 59. The inductance 66 and an inductance 56 are coupled with the inductance 52. However, the coupling between the inductances 66 and 50 is closer than that between the inductances 66 and 52 and the inductances 50 and 52. One end of the inductance 66 is connected to the shield 30 and lead 69, and the other end of the inductance 66 is connected to a cathode or electron emitting element 68 of the thermionic tube 56. An anode or plate electrode 10 of the thermionic tube 56 is connected to a suitable lead 38 that is adapted to be connected to a source of potential in a manner similar to that previously explained for the lead 38 of Fig. 1. A heater element 12 of the thermionic tube 56 is provided with suitable leads 42 and 44 similar to those of Fig. 1.

With particular reference to Figs. 3 and 4, the structure shown is a form preferable for the embodiment of the circuit of Fig. 1, and reference numerals similar to those used in Fig. 1 I The shield 30 is made in the form of a cup that serves as a base for the unit as well as a housing and mounting forthe parts thereof. A socket 80 is secured to the end of the cupshaped shield 36 by means of rivets such as 82. The socket 80, adapted to receive the tube I6,'is for supporting the tube. The socket 80 is provided with terminals such as 84, 86, 88 and 96 for making connections to the elements of the thermionic tube [6, and a lead 92 provided with a clip 94 and extending thru a grommet or eyelet 96 in the end of the cupshaped shield 30 is provided for making connection to the grid or control electrode terminal 98 of the thermionic tube l6. A grommet I preferably made of insulating material is mounted in a suitable aperture in the side of the cup-shaped shield for the protection of the leads 2, 38, 24, 44

and 42 that extend therethrough. The lead 2 connects to the shield 30. The leads 42 and 44 connect to the heater connection terminals such as 90-on the socket 80, and are preferably twisted so as' toneutralize or preventthe radiation of 'an- 'alternating field therefrom. The lead 24 connects-to a terminal I02 on a coil form I04 to provide 'fortheconnection between oneend of the primarycoil for inductance I2 and the-antenna post or terminal on the broadcast receiver. The lead 38 connects to the anodeor plate connecting terminal 80- on the socket 80, and the resistor 36 is connected between that anode or plate-terminal B8 and the auidliary or screen grid terminal 36. The cathode orelectron emitting element connector terminal84isconnected thru-a:lead I06 to atermin'al I08 o-n the coil I'form I 04. I

A strip'of-insulating material I I .formsa support for the parts other than those mounted directly on the shield 30 or socket 80, and'that "stripof insulating material or support I I0 is posiltioned withinthe cup-shaped shield 30 between ribs'zl II at its ends. The ribs III may beformed in the shield'or held in place by anysuitable meansxsuch as soldering. A rivetor othersuit- -able'fastening means II2 securesa lug H4, a .strip'of insulating material II 8 and a resilient condenser plate I to the strip of insulating ma- .terialuor support IIIJnear one endof that strip 'orrsupport. The rivet or'fastening means II2 alsoimakes an electrical connection between the lug -I I4 and the resilient plate I20. Then, the lug :II4 issoldered tothe shield element so thatit. aids in holding the strip of insulating materialor support H0 in position, and at the same .timefconnects the resilient-plate 20 to the shield :element '30. A lead. I22 makes a connection between the "common terminal of the inductances "12,20 and .:I0 and the shield element 30. A stationary condenser plate I I6 is preferably secured to'the strip of insulating material I I0 intermediatethestrip of insulating'materialill8 and the stripof insulating material or supportIII), and :is spaced or insulated from the rivet H2. Then, 'azscrew or other suitable connecting or fasten- .ing means I24 providedwith anut 125 and'a Washer-I28 secures the stationary condenserzplate I I6 'to the strip .of insulating material .II at near itsr'other -:end, and makes electrical. connection therewith. Thescrew I24.also.makes electrical :connection with a lugor connector I30 of a confdenser 'IB so as to provide aconnection between thetstationary plate I l6 and one side ofxthecondenser I 8,and to secure the condenser IBin positionton theinsulating support I'IIl. ".Theresistor --20:is'connected across the condenser I8 and supportedxbyitsconnection to the lug I301and1a lug I32of :the condenser I8. 'Alead'l34 connected atone end to a terminal I36'and'at its other end itoithe screw I24 forms a connectionbetween one iend'the inductance. or coil .20 and thecondenser .IB and'the-stationaryplate 'I I5. A collar I38 is .secured'to the shield element 30 and has a screw I40 threaded therein. The screw I40 has one endurging against'the resilient plate I20, and extends thru the collar I38 and shield 30 sothat its other end'is outside the shield element 30. The end of the screw I I-0 that'is outside the shield element 30 is provided with 'an insulating knob I42. andalock nut I44 that aids in looking the knob I42 in position on the screw I40, so that by manually turning'the knob I42, the screw I40 serves to adjust the position of the resilient plate I 20, and hence to tune the circuit.

With particular reference to Fig. 5, terminals I02, I08, I36 and I46 are preferably-secured to the "c'oil-Jform=l-04,-and in the present preferred'modisame groove 01 I'ECSSS.

ficationthose terminals'are in the form of pins securedtothe formiI04 by drivingthose pins into the form. .All of theinductances or coilswnecessary forthe operation of the present device are wound in suitable grooves or recesses I50 and I52 out or formedin thesurface of theform I04. The Jleads from, or ends of, the respectiveinductances or coils are then connected'to their particular pins or terminals. The pin or terminal I46 forms a commonterminalfor one end or lead from each of theinductances, while the pin or terminal I02 provides a terminal for the other end of the primary coil or inductance I2, .thepin or terminal I08 forms the terminal for the other end of the feed-back coil 26, and the pin orterminal I30 formsa terminal for the other end of the tuning coil orinductance I0. An aperture l iflisprovidedin one end of the form I44:f0.r'the accommodation of a mounting screw.

With particular reference to Fig. 6, reference numerals previously used andexplained refer to similar parts. However, in this .view it may be seen that the feed-back coil or inductance 26 is wound in the bottom of the groove or recess I52 and the primary. coil or inductance I2 is wound over the feed-back coil or inductance 26 in the The tuning coil or' inductance I0 is wound in a groove or recess I50. It'has been found that all of .these coils or inductances may be jumble-wound. The coils are all wound in the same direction. The form I04 is secured to the strip of insulating material or support II 0 by means of a screw I54, and'an aperture I 56 is provided through the stationarytplate H6 and the strip of insulating material I I8 to permit passage of the head of the screw I54 therethrough. Hence, it may be seenthat a'subassembly formed with the partthat is shown in Fig. 5 may be assembled and some of the connections made between the parts before the subassembly is placed within the shield element 30, thus leading to ease in manufacture and assembly.

1 In the operation of the unit, signals are picked up by the antenna Iand carried by the lead-2 to primary coil or inductance I2, and thence through the lead 24'to theantenna terminal of an ordinary or conventional broadcast :receiver. The potentials for the heater 40 and anode 'or plate electrode 32 of the thermionic tube I5 are preferably provided through the leads 42 and 44 for the heater, and 38 for the anode or plate electrode .32 respectively, from the broadcast receiver. The potential for the screen orauxiliary grid 34 is also provided from the lead 38 through the resistor 36. The potential drop across the resistor 38 causes the potential of the screen or auxiliary grid 34 to be somewhat lower than that of the anode or plate electrode 32. Theheat. of the element 40 conducted to thecathode or electron emitting The tuningor varying of theresonant frequency of theresonant circuit'4 is accomplished by tuning, or varying the capacity of the variable condenser 22. The resonant'frequency to which the resonant circuit '4 is tuned controls the action of: thengrid or control electrode I 4, and1the oscillating frequency of the circuit. Regeneration, which effects oscillatory action or oscillation of the circuit, is accomplished thru the .action of the feed-back coil or inductance 26 that is connected in series with the cathode or electron emitting element 28 and magnetically coupled with the inductances I0 and I2. It is particularly the coupling between the inductances 26 and ID that provides the regeneration to effect the'oscillatory action of the circuit. In considering the operation, it may be understood that the grid controls the cathode current as well as the plate current since the stream of electrons flowing from the cathode to the plate is what is actually controlled, and a change in this flow effected by the grid or control electrode affects both the plate and cathode currents. Consequently, by reactively or electromagnetically coupling the cathode and grid circuits through the coupling between the inductances 25 and Land properly regulating or establishing that coupling and the inductance values, the circuit including the tube It acts as an oscillation generator, the frequency of the oscillations of which are controlled by the values of the inductance l0 and condenser 22. By accomplishing this regeneration or regenerative action with the inductance 26 in the cathode circuit instead of in the usual manner of having an inductance in the anode or plate circuit, the potential difference between the turns of the feedback coil or inductance is kept low, and it is possible to have the common low potential connectionfor the inductances of the unit which prevents any potential difference of detrimental magnitude between the various inductances, and aids regeneration. The common connection between inductances also permits the connection of a common point in each of the inductances to the shield element which reduces stray capacities between the units and variations resulting therefrom, as well as reducing or eliminating the eifect of body-capacity in tuning.

Since the inductances l2 and 26 aremounted in the same groove or recess in the, form as best shown on Fig. 6, the coupling between those inductances is closer thanthe coupling between the inductances l0 and i2 and the inductances l0 and 26. However, due to the comparatively short distance between the inductances Wand l2 and the inductances I0 and 26, there is coupling between those inductances. Due to this coupling between the inductances, the oscillating energy generated in the thermionic tube It is mixed with the signals or signal energy picked up by the antenna l and transmitted to the inductance coil. This mixture of signal and oscillating energy produces beat frequency signals, the frequencies "of which are equal to the difference of the signal frequency and oscillator frequency.

Hence, if the tuning elements of the broadcast receiver are set to a fixed position, so that it excludes signals of a frequency other than that to which it is tuned, the beat frequency signals of a frequency to which the broadcast receiver is tuned are amplified and reproduced by the broadcast receiver. Since variation of the capacity of the condenser 22 varies the resonant frequency of the resonant circuit 4, and consequently the oscillator frequency, various signals may be selected by tuning thecondenser 22 so that the beat frequency produced with the selected signal is equal to the frequency to which the broadcast receiver is tuned. Since broadcast signals within the frequency range of the broadcast receiver itself are picked up by the antenna I at the same time the other signals are picked up, it is necessary, in order to prevent their reception and reproduction by the broadcast receiver, to tune that receiver to a frequency at which no broadcast signals are received. At' times when it is desired to receive a broadcast program, and yet have a notice or warning when a short wave station that transmits signals intermittently is transmitting, the broadcast receiver may be set so that it receives the desired program, and then the condenser 22 may be set so that the oscillator frequency will be such that when the short wave station is transmitting, a heterodyne signal in the form of a whistle will be received. The short wave station may then be received by tuning the broadcast receiver away from the broadcast program and to a point at which the short Wave station is clearly received.

Since the oscillator also generates harmonic frequencies that are multiples of its fundamental frequencies, it is possible by properly choosing the oscillator frequency and the frequency to which the broadcast receiver is tuned, to receive signals in different short wave frequency bands without materially changing the oscillator circuit. That is, for example, if the broadcast receiver is set to receive a signal frequency of 600 kilocycles, and the oscillator is designed so that its frequency which is governed by the constants of the resonant circuit 4, may be varied from 1600 kilocycles to 2300 kilocycles, a signal having a frequency of 2400 kilocycles may be received by tuning the resonant circuit 4 so that the fundamental frequency of the oscillator is 1800 kilocycles. Then, the signal in a different frequency band, such as one having a frequency of 400 kilocycles may be received by adjusting the resonant frequency of the resonant circuit 4 so that its fundamental frequency is 1700 kilocycles and its second harmonic frequency is consequently 3400 kilocycles. It may be noted that in the first instance the difference between the signal frequency and the oscillator frequency was equal to the frequency to which the broadcast receiver was tuned, and in the second instance the difference between the signal frequency and the oscillator second harmonic frequency was equal to the frequency to which the broadcast receiver was tuned.

The modified circuit shown in Fig. 2 operates in substantially the same manner as the circuit shown in Fig. 1, and the regeneration or oscillatory action is accomplished in substantially the same manner. However, in this circuit the different type of tubes has been shown and the resistor or grid leak 64 is connected across the condenser, 58 thru the inductance 52. In this circuit also, the primary coil or inductance 50 is magnetically coupled with the inductances 66 and 52, but does not have the terminal or end connected to the common terminal of the inductances 52 and 60.

Either the circuit shown in Fig. 1 or that shown in Fig. 2 could very well be made into a unit as shown in Figs. 3 and 4, although the particular structure of Fig. 4 shows a unit embodying the circuit of Fig. 1. In this type of unit, the inductances may be jumble wound on a form such as that shown in Fig. 5, and in a way more fully disclosed in Fig. 6. Then, the condenser may preferably be formed as shown in Fig. 6 with a stationary plate H6 cemented or otherwise secured to a strip or sheet of insulating material I I8. The other plate of the condenser I20 is made of resilient material that is normally biased so as to flex away from the plate I l 6. The capacity of the condenser is then a minimum when the plate I20 is fully flexed-away fromtheplate' H6: To facilitate'ease of assembly; the-inductance unit shown in Fig. 5 is secured'to the strip of insulating-material orthe mounting H 0-.- The resistor 20 'andcondenser I6, as well as the variable condenser formed by plates H6 and |20 are also secured to the mounting H0 and the connections made between the parts or" the subassembly thus formed'before the subassembly is placed'in the base formed by the shield element'30. The socket wand resistor 36 are secured to the baseor shield element 30 and the leads 2, 42, 44*and38connected to their respectiveterminals before the subassembly is put in place. The strip of insulating material or mounting H0 is positioned" by means of'ribs lil'. The screw'l ifiis'threaded into the collar" l38 that'is secured to the shield element 3t, and servesas a means. of adjusting the distance between the plates H6 and I29 to vary the capacity of. the condenser formed thereby, The insulating knob l42"is'provided onthe screw I40 outside of the shield element 30'to facilitate manual adjustment of the. capacity of the variable condenser to accomplish the tuning of the unit as described for Fig. 1;

The leads 2, 24, 38, Hand. are provided for making connections with the? broadcast receiver as shown in Fig. 1. After thus being connected,

the operation is substantially as previously described.

Although the invention illustrated and described represents a preferred form or embodiment, others may be used, all coming within the scope and spirit of the claims which follows.

What is claimed is:

1. A short Wave adapter for a broadcast receiver having an antenna therefor and an antenna terminal thereon comprising in combination, a thermionic tube having an anode, a control electrode, an auxiliary grid, a cathode, and a heater element therein; a resistor connected between said anode and said auxiliary grid; a lead connected to the anode for applying a potential to said anode; a shield element; a grid condenser and grid leak; a tuning inductance having one end connected to said control electrode thru said grid condenser and grid leak and its other end connected to said shield; a variable condenser connected across the tuning inductance and forming a tunable resonant circuit therewith; a feed-back coil having one end connected to said cathode and its other end connected to the shield; a primary inductance having one end connected to the shield and adapted to be connected to said antenna and its other having a lead thereon adapted to be connected to said antenna terminal; and means for applying a heating potential to said heater element; said inductances being magnetically coupled, with the coupling between said primary inductance and said feed-back inductance closer-than the coupling between the tuning and feed-back inductances.

2. A short wave adapter for a broadcast receiver having an antenna therefor and an antenna terminal thereon, comprising in combination, a thermionic tube having an anode, a control electrode, a cathode, and a heater element therein; a lead connected to said anode for applying a potential to said anode; a shield element; a grid condenser, a tuning inductance having one end connected to said control electrode thru said grid condenser and its other end connected to said shield; a variable condenser connected across the-turning inductance andforminga tunable resonant circuit therewith; a resistor connected acrosssaid tuning inductance and gridcondenser; a feed-back coil having one end connected to said cathode and its other endconnected to the shield; a primary inductance havingone end with alead thereon for-'making connection to said antenna and its other end having a lead thereon for making connection to said antenna terminal; and means for applying a heating potential to said heater element; said-inductancesbeing magcondenser a second inductance having 5 an end 7 connected to said electron emitting eler'nent and its other end connected to an end of 'said first'im ductance a primaryinductance l coupled to said inductances and having leads connected to its ends for making connection with said antenna and. said antenna terminal; and a variable condenser connected across said first inductance and forming a tunable resonant circuit therewith.

4. A short wave adapter for a broadcast receiver having an antenna therefor and an antenna terminal thereon comprising in combination, a thermionic tube having an anode, a control electrode, an auxiliary grid, a cathode, and a heater element therein; a resistor connected between said anode and said auxiliary grid; a lead connected to the anode for applying a potential to said anode; a shield element; a grid condenser and grid leak; a tuning inductance having one end connected to said control electrode thru said grid condenser and grid leak and its other end connected to said shield; a variable condenser connected across the tuning inductance and forming a tunable resonant circuit therewith; a feedback coil magnetically coupled to the tuning inductance and having one end connected-to said cathode and its other end connected to the shield;

a primary inductance magnetically coupled to the tuning inductance and having one end connected to the shield and adapted to be connected to said antenna and its other having a lead thereon adapted to be connected to said antenna terminal; and means for applying a heating potential to said heater element.

5. A short Wave adapter for a broadcast receiver having an antenna therefor and an antenna terminal thereon, comprising in combination, a thermionic tube having an anode, a control electrode, a cathode, and a heater element therein; a lead connected to said anode for applying a potential to said anode; a shield element; a grid condenser; a tuning inductance having one end connected to said control electrode thru said grid condenser and its other end one end connected to said cathode and its other end connected to the shield; a primary inductance magnetically coupled to the secondary inductance and having one end with a lead thereon for making connection to said antenna and its other end having a lead thereon for making connection to said antenna terminal; and means for applying a heating potential to said heater element.

6. In a unitary radio device, the combination comprising, a plurality of inductances Wound on a form and including a primary inductance, a tuning inductance and a feed-back inductance, said inductances being provided with terminals secured to said form; a variable condenser connected across said tuning inductance to form a tunable resonant circuit; a thermionic tube having an anode, a control electrode, an auxiliary grid, a cathode, and a heater therein; a grid leak and grid condenser for coupling said tunable resonant circuit to said control electrodeya cup shaped shield element; a socket secured to the end of said cup-shaped shield for holding said tube and making connections thereto; said variable condenser, inductances, and grid leak forming a ,subassembly and mounted within said shield;

means extending to the outside of said shield for adjusting said variable condenser; said shield forming a base for said device; and leads extending outside said shield from the ends of saidprimary inductance, said heater, and said anode for making connections thereto.

'7. In a unitary radio device, the combination comprising, a plurality of coupled inductances Wound on a form and including a primary inductance, a tuning inductance and a feed-back inductance; said inductances having a common connection, which common connection is at a low D. C. potential; a variable condenser connected across said tuning inductance to form a tunable resonant circuit; a thermionic oscillator tube having an anode, a control electrode, and an electron emitting element therein; means coupling said control electrode to said tunable resonant circuit to control the frequency of oscillations of said thermionic tube; a cup-shaped shield element; a socket secured to the end of said cup-shaped shield for holding said tube and making connection to one of said electrodes and said element, said shield forming a base for said device; said variable condenser and said inductances mounted within said cup-shaped shield; means extending to the outside .of said shield for adjusting said variable condenser.

ROBERT F. ZIMMERMAN. HERBERT W. DE WEESE. 

